On-body microsensor for biomonitoring

ABSTRACT

A microsensor and method of manufacture for a microsensor, comprising an array of filaments, wherein each filament of the array of filaments comprises a substrate and a conductive layer coupled to the substrate and configured to facilitate analyte detection. Each filament of the array of filaments can further comprise an insulating layer configured to isolate regions defined by the conductive layer for analyte detection, a sensing layer coupled to the conductive layer, configured to enable transduction of an ionic concentration to an electronic voltage, and a selective coating coupled to the sensing layer, configured to facilitate detection of specific target analytes/ions. The microsensor facilitates detection of at least one analyte present in a body fluid of a user interfacing with the microsensor.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.17/125,999, filed Dec. 17, 2020 (U.S. Pat. No. 11,197,985), which is acontinuation of U.S. application Ser. No. 16/886,742, filed May 28, 2020(U.S. Pat. No. 11,123,532), which is a continuation of U.S. applicationSer. No. 16/722,977, filed Dec. 20, 2019, which is a continuation ofU.S. application Ser. No. 14/876,692, filed Oct. 6, 2015 (U.S. Pat. No.10,549,080), which is a continuation of U.S. application Ser. No.14/211,404, filed Mar. 14, 2014 (U.S. Pat. No. 9,182,368), which claimspriority to U.S. Provisional Application No. 61/905,583, filed Nov. 18,2013 and U.S. Provisional Application No. 61/781,754, filed Mar. 14,2013, all of the aforementioned applications are herein incorporated byreference in their entireties.

TECHNICAL FIELD

This invention relates generally to the medical device field, and morespecifically to a new and useful on-body multi-analyte microsensor forbiomonitoring.

BACKGROUND

Biomonitoring devices are commonly used, particularly byhealth-conscious individuals and individuals diagnosed with ailments, tomonitor body chemistry. Conventional biomonitoring devices typicallyinclude analysis and display elements. Such biomonitoring devicesperform the tasks of determining one or more vital signs characterizinga physiological state of a user, and provide information regarding theuser's physiological state to the user. In variations, biomonitoringdevices can determine an analyte level present in a user's body, andprovide information regarding the analyte level to the user; however,these current biomonitoring devices typically convey information tousers that is limited in detail, intermittent, and prompted by thecommand of the user. Such biomonitoring devices, including blood glucosemeters, are also inappropriate for many applications outside ofintermittent use, due to design and manufacture considerations.Additionally current devices are configured to analyze one or a limitednumber of analytes contributing to overall body chemistry, due tolimitations of sensors used in current biomonitoring devices.

There is thus a need in the medical device field to create a new anduseful on-body microsensor for biomonitoring. This invention providessuch a new and useful microsensor.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1A depicts an embodiment of a microsensor for biomonitoring;

FIG. 1B depicts an embodiment of an array of filaments, and amicrosensor coupled to an electronics module;

FIG. 2A depicts an embodiment of a filament for biomonitoring;

FIG. 2B depicts another embodiment of a filament for biomonitoring;

FIGS. 2C and 2D depict examples of filaments for biomonitoring;

FIG. 2E depicts an example of a filament, comprising an adhesion layer,for biomonitoring;

FIG. 2F depicts an example of a filament, comprising a temporaryfunctional layer, for biomonitoring;

FIGS. 3A-3H depict embodiments of filament geometries;

FIG. 4 depicts an embodiment of a manufacturing method for an on-bodymicrosensor for biomonitoring;

FIGS. 5A-5C depict embodiments of a portion of a manufacturing methodfor an on-body microsensor for biomonitoring;

FIGS. 6A and 6B depict variations of forming a filament substrate;

FIGS. 7A-7D depict variations of defining an active region and anon-active region of the filament with an insulating layer;

FIGS. 8A-8E depict variations of a portion of an embodiment of a methodfor an on-body microsensor for biomonitoring; and

FIG. 9 depicts a portion of an embodiment of a method for an on-bodymicrosensor for biomonitoring.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description of the preferred embodiments of the inventionis not intended to limit the invention to these preferred embodiments,but rather to enable any person skilled in the art to make and use thisinvention.

1. Microsensor

As shown in FIGS. 1A, 2A, and 2B, an embodiment of a microsensor 100comprises an array of filaments 110, wherein each filament 120 of thearray of filaments 110 comprises a substrate 130 and a conductive layer140 configured to facilitate analyte detection. Alternatively, thesubstrate 130 itself can be conductive with no additional conductivelayer 140. Each filament 120 of the array of filaments 110 can furthercomprise an insulating layer 150 configured to isolate regions foranalyte detection, a sensing layer 160 configured to enable transductionof an ionic concentration to an electronic voltage, and a selectivecoating 170 configured to facilitate detection of specific targetanalytes/ions. Any filament 120 of the array of filaments 110 canfurther comprise an adhesion coating 180 configured to maintain contactbetween layers, coatings, and/or substrates of the filament 120, and atemporary functional layer 190 configured to facilitate penetration of afilament into the body. The microsensor 100 and the array of filaments110 thus function to penetrate a user's skin in order to sense at leastone target analyte characterizing the user's body chemistry. Preferably,the microsensor 100 is configured to be worn by a user, such thatcontinuous or semi-continuous monitoring of the user's body chemistry isenabled; however, the microsensor 100 can alternatively be usedintermittently to sense analytes characterizing the user's bodychemistry. Preferably, the microsensor 100 is configured to penetratethe user's stratum corneum (e.g., an outer skin layer) in order to senseanalytes characterizing the user's body chemistry in the user'sinterstitial (extracellular) fluid; however, the microsensor 100 canalternatively be configured to penetrate deeper layers of a user's skinin order to sense analytes within any appropriate bodily fluid of theuser, such as the user's blood. The microsensor 100 can be configured tosense analytes/ions characterizing a user's body chemistry using apotentiometric measurement (e.g., for analytes including potassium,sodium calcium, alcohol, cortisol, hormones, etc.), using anamperometric measurement (e.g., for analytes including glucose, lacticacid, creatinine, etc.), using a conductometric measurement, or usingany other suitable measurement.

As shown in FIG. 1B, the microsensor 100 can also be coupled to anelectronics module 115, such that sensed analytes result in a signal(e.g., voltage, current, resistance, capacitance, impedance,gravimetric, etc.) detectable by the electronics module 115; however,analyte sensing can comprise any other appropriate mechanism using themicrosensor 100. In an embodiment wherein the microsensor 100 is coupledwith an electronics module 115, the microsensor 100 can also beintegrated with the electronics module 115, in variations wherein theelectronics module 115 is characterized by semiconductor architecture.In a first variation, the microsensor 100 is coupled to thesemiconductor architecture of the electronics module 115 (e.g., themicrosensor 100 is coupled to an integrated circuit comprising theelectronics module 115), in a second variation, the microsensor 100 ismore closely integrated into the semiconductor architecture of theelectronics module 115 (e.g., there is closer integration between themicrosensor 100 and an integrated circuit including the electronicsmodule 115), and in a third variation, the microsensor 100 and theelectronics module 115 are constructed in a system-on-a-chip fashion(e.g., all components are integrated into a single chip). As such, insome variations, filaments 120 the array of filaments 110 of themicrosensor 100 can be directly or indirectly integrated withelectronics components, such that preprocessing of a signal from themicrosensor 100 can be performed using the electronics components (e.g.,of the filaments 120, of the electronics module 115) prior to or aftertransmitting signals to the electronics module 115 (e.g., to an analogto digital converter). The electronics components can be coupled to afilament substrate, or otherwise integrated with the filaments in anysuitable fashion (e.g., wired, using a contact pad, etc.).Alternatively, the electronics components can be fully integrated intothe electronics module 115 and configured to communicate with themicrosensor 100, or the electronics components can be split between themicrosensor and the electronics module 115. The microsensor 100 can,however, comprise any other suitable architecture or configuration.

The microsensor 100 preferably senses analyte parameters using the arrayof filaments 110, such that absolute values of specific analyteparameters can be detected and analyzed. The microsensor 100 canadditionally or alternatively be configured to sense analyte parametersusing the array of filaments 110, such that changes in valuescharacterizing specific analyte parameters or derivatives thereof (e.g.,trends in values of a parameter, slopes of curves characterizing a trendin a parameter vs. another parameter, areas under curves characterizinga trend, a duration of time spent within a certain parameter range,etc.) can be detected and analyzed. In one variation, sensing by themicrosensor 100 is achieved at discrete time points (e.g., every minuteor every hour), and in another variation, sensing by the microsensor 100is achieved substantially continuously. Furthermore, sensing can beachieved continuously, with signal transmission performed in a discreteor non-discrete manner (e.g., prior to or subsequent to processing of asignal). In one specific example for blood chemistry analysis, the arrayof filaments 110 of the microsensor 100 is configured to sense at leastone of electrolytes, glucose, bicarbonate, creatinine, blood ureanitrogen (BUN), sodium, and potassium of a user's body chemistry. Inanother specific example, the array of filaments 110 of the microsensor100 is configured to sense at least one of biomarkers, cell count,hormone levels, alcohol content, gases, drug concentrations/metabolism,pH and analytes within a user's body fluid.

1.1 Microsensor—Array of Filaments

The array of filaments 110 functions to interface directly with a userin a transdermal manner in order to sense at least one analytecharacterizing the user's body chemistry. The array of filaments can bean array of fibers, an array of pillars, an array of microneedles,and/or any other suitable array configured to facilitate analytedetection in a user. The array of filaments no is preferably arranged ina uniform pattern with a specified density optimized to effectivelypenetrate a user's skin and provide an appropriate signal, whileminimizing pain to the user. However, the array of filaments 110 canadditionally or alternatively be coupled to the user in any othersuitable manner (e.g., using an adhesive, using a coupling band/strap,etc.). Additionally, the array of filaments 110 can be arranged in amanner to optimize coupling to the user, such that the microsensor 100firmly couples to the user over the lifetime usage of the microsensor100. For example, the filaments 120 can comprise several pieces and/orbe attached to a flexible base to allow the array of filaments 110 toconform to a user's body. In one variation, the array of filaments 110is arranged in a rectangular pattern, and in another variation, thearray of filaments 110 is arranged in a circular or ellipsoid pattern.However, in other variations, the array of filaments 110 can be arrangedin any other suitable manner (e.g., a random arrangement). The array offilaments no can also be configured to facilitate coupling to a user, bycomprising filaments of different lengths or geometries. Havingfilaments 120 of different lengths can additionally or alternativelyfunction to allow measurement of different ions/analytes at differentdepths of penetration (e.g., a filament with a first length may senseone analyte at a first depth, and a filament with a second length maysense another analyte at a second depth). The array of filaments no canalso comprise filaments 120 of different geometries (e.g., height,diameter) to facilitate sensing of analytes/ions at lower or higherconcentrations. In one specific example, the array of filaments 110 isarranged at a density of 100 filaments per square centimeter and eachfilament 120 in the array of filaments no has a length of 250-350microns, which allows appropriate levels of detection, coupling to auser, and comfort experienced by the user. In variations of the specificexample, a filament 120 in the array of filaments 120 can have a lengthfrom 0-1000 μm, or more specifically, a length from 150-500 μm.

Each filament 120 in the array of filaments 110 preferably functions tosense a single analyte; however, each filament 120 in the array offilaments 110 can additionally be configured to sense more than oneanalyte. Furthermore, the array of filaments 110 can be furtherconfigured, such that a subarray of the array of filaments 110 functionsas a single sensor configured to sense a particular analyte orbiomarker. As shown in FIG. 1B, multiple subarrays of the array offilaments 110 may then be configured to sense differentanalytes/biomarkers, or the same analyte/biomarker. Furthermore, asubarray or a single filament 120 of the array of filaments 110 can beconfigured as a ground region of the microsensor 100, such that signalsgenerated by the microsensor 100 in response to analyte detection can benormalized by the signals generated by the subarray or single filament120 serving as a ground region. Preferably, all subarrays of the arrayof filaments 110 are substantially equal in size and density; however,each subarray of the array of filaments 110 can alternatively beoptimized to maximize signal generation and detection in response to aspecific analyte. In an example, analytes that are known to have a lowerconcentration within a user's body fluid (e.g., interstitial fluid,blood) can correspond to a larger subarray of the array of filaments110. In another example, analytes that are known to have a lowerconcentration within a user's body fluid can correspond to a smallersubarray of the array of filaments 110. In one extreme example, anentire array of filaments can be configured to sense a single analyte,such that the microsensor 100 is configured to sense and detect only oneanalyte.

In other variations, a subarray of the array of filaments 117 can alsobe used to detect other physiologically relevant parameters, includingone or more of: electrophysiological signals (e.g., electrocardiogram,electroencephalogram), body temperature, respiration, heart rate, heartrate variability, galvanic skin response, skin impedance change (e.g.,to measure hydration state or inflammatory response), and any othersuitable biometric parameter. In these other variations, the subarraywould be dedicated to measuring these physiologically relevantparameters, which could be combined with analyte/ion parametermeasurements in order to provide meaningful information to a user. As anexample, the simultaneous measurement of potassium levels andelectrocardiogram measurements, enabled by subarrays of the array offilaments 117, may provide a more complete diagnosis of cardiovascularproblems or events than either measurement by itself.

1.2 Microsensor—Filament

As shown in FIG. 2A, each filament 120 of the array of filaments 110comprises a substrate 130 and a conductive layer 140 configured tofacilitate analyte detection. Each filament 120 of the array offilaments 110 can further comprise an insulating layer 150 configured toisolate regions for analyte detection, a sensing layer 160 configured toenable transduction of an ionic concentration to an electronic voltage,and a selective coating 170 configured to facilitate detection ofspecific target analytes. As shown in FIG. 2E, each filament can furthercomprise an adhesion coating 180 configured to maintain contact betweenlayers, coatings, and/or substrates of the filament 120, and/or atemporary functional layer 190, as shown in FIG. 2F, configured tofacilitate penetration of a filament 120 into the body. A filament 120thus functions to directly penetrate a user's skin, and to sensespecific target analytes/ions characterizing the user's body chemistry.

The substrate 130 functions to provide a core or base structure uponwhich other layers or coatings can be applied, in order to facilitateprocessing of each filament 120 for specific functionalities. As such,the material of which the substrate 130 is composed can be processed toform at least one protrusion as a substrate core for a filament 120,including a base end coupled to the substrate 130 bulk and a tip at thedistal end of the substrate core, that facilitates access to a bodyfluid of the user. Alternatively, the substrate 130 can be coupled to aprotrusion (e.g., as a piece separate from the substrate) or aprotrusion can be grown from a surface of the substrate 130 in any othersuitable manner. Preferably, the material of the substrate 130 isprocessable to form an array of protrusions as substrate cores for thearray of filaments 110; however, the material of the substrate 130 canalternatively be processable in any other suitable manner to form anyother suitable filament structure. Preferably, the substrate 130 has auniform composition; however, the substrate 130 can alternatively have anon-uniform composition comprising regions or layers configured tofacilitate processing of subsequent functional layer/coating additions.The substrate 130 can be composed of a semiconducting material (e.g.,silicon, quartz, gallium arsenide), a conducting material (e.g., gold,steel, platinum, nickel, silver, polymer, etc.), and/or an insulating ornon-conductive material (e.g., glass, ceramic, polymer, etc.). In somevariations, the substrate 130 can comprise a combination of materials(e.g., as in a composite, as in an alloy). Furthermore, in variationswherein the substrate 130 is non-conductive, a fluid path defined at thesubstrate 130 (e.g., a fluid channel, a groove, a hollow region, anouter region, etc.) and coupled to a conductive layer 140 (e.g., aconductive base region, a conductive core, a conductive outer layer) canenable signal transmission upon detection of an analyte/analyteconcentration. In a specific example, the substrate 130 is composed ofP-type, boron-doped, <100> orientation silicon with a resistivity of0.005-0.01 ohm-cm, a thickness from 500-1500 μm, a total thicknessvariation (TTV) of <10 μm, with a first surface side polish. Invariations of the specific example, the substrate 130 can be composed ofsilicon with any other suitable type, doping, miller index orientation,resistivity, thickness, TTV, and/or polish. Furthermore, the substrate130 can be processed using semiconductor processing methods, machiningmethods, manufacturing processes suited to a ductile substrate material,and/or manufacturing methods suited to a brittle material.

The conductive layer 140 functions to provide a conductive “active”region to facilitate signal transmission upon detection of an analyte bya filament 120. The conductive layer 140 can comprise a layer of asingle material, or can alternatively comprise multiple materials (e.g.,multiple layers of one or more materials). In variations, the conductivelayer 140 can include any one or more of: a platinum-based material, aniridium-based material, a tungsten-based material, a titanium-basedmaterial, a gold-based material, a nickel-based material, and any othersuitable conductive or semiconducting material (e.g., silicon, dopedsilicon). Furthermore, the layer(s) of the conductive layer 140 can bedefined by any suitable thickness that allows signal transmission upondetection of an analyte by the filament 120. In a first specificexample, the conductive layer 140 includes a 1000 Å thick platinumlayer, a 1000 Å thick iridium layer, a 1000 Å thick tungsten layer, anda 100 Å thick titanium nitride layer. In a second specific example, theconductive layer 140 includes a 1000 Å thick platinum layer and a 100 Åthick titanium layer. In a third specific example, the conductive layer140 includes a 1000 Å thick platinum layer and a 100 Å thick titaniumnitride layer. In a fourth specific example, the conductive layer 140includes a 1000 Å thick iridium layer and a 100 Å thick titanium nitridelayer. In a fifth specific example, the conductive layer 140 includes a1000 Å thick tungsten layer. In a sixth specific example, the conductivelayer 140 includes one or more of: nickel, gold, and platinum (e.g.,deposited by electroplating). Preferably, the conductive layer 140 onlycovers a portion of the substrate 130 (e.g., a substrate core)contacting the user's body fluids, thus forming an “active region” ofthe filament 120, and in one variation, covers a tip region of eachfilament 120 (e.g., a tip of a substrate core); however, the conductivelayer 140 can alternatively cover the entire surface of the substrate130 contacting a user's body fluids. In variations wherein the substrate130 is conductive, the filament 120 can altogether omit the conductivelayer 140. Furthermore, in variations wherein the substrate 130 isnon-conductive, a fluid path defined at the substrate 130 (e.g., a fluidchannel, a groove, a hollow region, an outer region, etc.) and coupledto a conductive layer 140 (e.g., a conductive base region, a conductivecore, a conductive outer layer) can enable signal transmission upondetection of an analyte/analyte concentration, as described above.

The insulating layer 150 functions to form an insulating region of afilament 120, and is configured to provide a “non-active” region of thefilament 120. Additionally, the insulating layer 150 functions to defineand/or isolate an “active” region of the filament 120. As such, theinsulating layer 150 preferably leaves at least a portion of theconductive layer 140 exposed to define the active region of the filament120. In one variation, the insulating layer 150 ensheathes the substratecore of each filament 120 in the array of filaments, and canadditionally or alternatively cover all exposed regions of the substrate130 to isolate areas of signal transmission. The insulating layer 150preferably includes an oxide layer that is grown at desired surfaces ofthe substrate (e.g., to a thickness of 0.1-10 μm), thereby forming theinsulating layer. However, the insulating layer 150 can additionally oralternatively include any other suitable material that is not removableduring removal of sacrificial layers used during processing of the arrayof filaments 110. As such, in other variations, the insulating layer 150can be composed of any one or more of: an insulating polymer (e.g.,polyimide, cyanate ester, polyurethane, silicone) that is chemicaland/or heat resistant, an oxide, a carbide, a nitride (e.g., of silicon,of titanium), and any other suitable insulating material. Preferably,the insulating layer 150 only covers a portion of the substratecontacting the user's body fluids, thus defining an “active region” ofthe filament 120 and a “non-active” region of the filament 120.Alternatively, the filament 120 can altogether omit the insulating layer150.

The sensing layer 160 functions to enable transduction of an ionicconcentration to an electronic voltage, to enable measurement ofanalyte/ion concentrations characterizing body chemistry. The sensinglayer 160 can also function to prevent unwanted signal artifacts due tooxygen fluxes in a user's body fluids. Furthermore, the sensing layer160 can also enable transduction of a molecular species concentrationthrough a current, capacitance, or resistance change. Preferably, thesensing layer is a conductive material with reversible redox reactionbehavior, such that detection of increased ion concentrations followedby decreased ion concentrations (or visa versa) can be enabled by thesensing layer 160. Additionally, the sensing layer 160 is preferably anappropriately bio-safe, anti-inflammatory, and anti-microbial material.The sensing layer 160 can be a polymer, such as polypyrrole orpolyaniline, which undergoes a reversible redox reaction characterizedby the following generic equation: P^((ox))+e−⇔P^((red)). The sensinglayer 160 can additionally or alternatively be composed of anyappropriate conductive material (e.g., sulfur-containing polythiophenes,silver chloride, etc.) that has reversible redox reaction behavior. Forexample, silver chloride undergoes a reversible redox reactioncharacterized by the following equation: AgCl+e−⇔Ag(s)⁺+Cl⁻. In eitherexample redox reaction equation, electron (e−) generation results inmeasurable signals corresponding to detected ion concentrations foranalyte detection, and further, the sensing layer 160 serves as areference electrode for ion concentration measurements based upon adetected voltage change across a selective coating 170 coupled to thesensing layer 160. However, in other variations, the sensing layer 160may not comprise a material with reversible redox reaction behavior, andother variations can further comprise a controlled ion coating (e.g.,poly-hydroxyl ethyl methacrylate prepared with potassium chloride) thatfunctions to form a portion of a reference electrode for ionconcentration measurements. Additionally or alternatively, the sensinglayer 160 can include molecules (e.g., glucose oxidase,phenylenediamine, gluteraldehyde, lysine, tyramine, trehalose, lipids,surfactants, etc.) that facilitate analyte detection. In one example,the sensing layer 160 includes electropolymerized phenylenediamene,tyramine, glucose oxidase, and poly-lysine to facilitate glucosesensing. The sensing layer 160 is preferably uniform over an activeregion of a filament 120 defined by the conductive layer 140 and theinsulating layer 150; however, the sensing layer 160 can alternativelynon-discriminately coat the surface of the filament 120, and/or can be anon-uniform coating. The sensing layer 160 can be maintained at a viablestate by packaging the microsensor 100 in a hydrated state; however, thesensing layer 160 can be alternatively be configured to equilibratewithin a short time period (e.g., less than one hour) upon coupling ofthe array of filaments 110 to a user. Alternative variations of thefilament may altogether omit the sensing layer 160.

The selective coating 170 functions to facilitate sensing of specifictarget analytes. The selective coating 170 preferably facilitatesion-selective reactions that generate signals reflective of ionconcentration; however, the selective coating 170 can additionally oralternatively facilitate enzyme reactions that generate changes insignals (e.g., current) due to binding of complementary molecules totarget analytes/ions. The selective coating 170 is preferablyanti-microbial and anti-inflammatory, and can additionally oralternatively include any other features that encourage biocompatibilityduring use by a user. Preferably, the selective coating 170 comprises atleast one complementary molecule 171 (e.g., ionophore, protein, peptide,amino acid, etc.) to a target analyte/ion distributed within a polymermatrix 172, as shown in FIG. 2A. Preferably, the complementary molecule171 is evenly dispersed throughout the polymer matrix 172; however, thecomplementary molecule 171 can alternatively be localized within regionsof the polymer matrix 172 in a heterogeneous manner. In examples, thecomplementary molecule is valinomycin/potassium tetrakis for potassiumsensing, 4-tert-Butylcalix[4]arene-tetraacetic acid tetraethyl ester forsodium sensing, (−)-(R,R)—N,N′-Bis-[11-(ethoxycarbonyl)undecyl]-N,N′,4,5-tetramethyl-3,6-dioxaoctane-diamide, DiethylN,N′-[(4R,5R)-4,5-dimethyl-1,8-dioxo-3,6-dioxaoctamethylene]bis(12-methylaminododecanoate) for calcium sensing, andmeso-Tetraphenylporphyrin manganese(III)-chloride complex for chloridesensing, according to ion-selective reactions. In an example, thepolymer matrix 172 is composed of polyvinyl chloride (PVC) with aplasticizer to affect flexibility of the polymer matrix; however, thepolymer matrix 172 can additionally or alternatively be composed of anyother suitable polymer (e.g., polyethylene, polytetrafluoroethylene,urethane, parylene, nafion, polyvinyl chloride, polyvinyl alcohol,polyvinyl butyral, polydimethylsiloxane, fluorinated polymers, celluloseacetate, etc.) or non-polymer (e.g., oxide, nitride, carbide, etc.)configured to contain a distribution of complementary molecules.Additionally, the selective coating 170 may not comprise a plasticizer.The selective coating 170 is preferably defined by a thickness thatcharacterizes a rate at which complementary molecules bind to targetanalytes (e.g., diffusion rate), and that also characterizes the amount(e.g., concentration or total amount) of complementary molecules withinthe selective coating 170. Additionally, the polymer matrix 172 cancontain additives and can additionally or alternatively be processed(e.g., with polar functional groups) to improve its adhesion to thefilament 120 and to prevent delamination as the filament 120 is insertedinto a user's skin. In examples, additives of the polymer matrix 172 caninclude amino-silicanes, polyhydroxy-ether imides, butylated silica, andheterogeneous oxidizers.

In other variations, the selective coating 170 of the filament 120 canadditionally or alternatively function to enable amperometric detectionof molecules (e.g., glucose, creatinine) using immobilized enzymes. Inthese variations, the selective coating 170 can be replaced by or mayfurther comprise a layer of immobilized enzyme (e.g., glucose oxidasefor glucose, creatine amidinohydrolase for creatinine) that functions tocatalyze a reaction of the analyte to produce a mediator species (e.g.,hydrogen peroxide), wherein the concentration of the mediatior speciescan be amperometrically detected via oxidation or reduction at a surfaceof the conductive layer 140 or the sensing layer 160. In one example,glucose is oxidized by glucose oxidase to generate hydrogen peroxide.The generated hydrogen peroxide is then hydrolyzed by a conductingsurface (e.g., a platinum conducting layer) while it is held at anelectric potential. In a variation of this example, the conductingsurface may alternatively not be held at an electric potential, forinstance, in cases wherein molecular or other species (e.g., ironhexacyanoferrate) serve as a layer of transduction. Furthermore, inother variations of this example, other oxidases (e.g. alcohol oxidase,D- and L-amino acid oxidases, cholesterol oxidase, galactose oxidase,urate oxidase, etc.) can be used in a similar manner for the analysis oftheir complements.

In variations of the sensing layer including a layer of immobilizedenzymes, the layer of immobilized enzymes can be covered by one or moremembranes, which functions to control the diffusion rate and/orconcentrations of analyte, mediator species (e.g., hydrogen peroxide,ferrocene), or interfering species (e.g., uric acid, lactic acid,ascorbic acid, acetaminophen, oxygen). The membrane(s) can also functionto provide mechanical stability. In examples, the membrane(s) caninclude any one or more of: polyurethanes, nafion, cellulose acetate,polyvinyl alcohol, polyvinyl chloride, polydimethylsiloxane, parylene,polyvinyl butyrate and any other suitable membrane material.

As shown in FIG. 2E, any filament 120 of the array of filaments 110 canfurther comprise an adhesion coating 180, which functions to maintaincontact between layers, coatings, and/or substrates of the filament 120.The adhesion coating 180 can further function to bond the layers,coatings, and/or substrates, and can prevent delamination between thelayers, coatings, and/or substrates. The adhesion coating 180 ispreferably an appropriately bio-safe, anti-inflammatory, andanti-microbial material, and preferably maintains contact betweenlayers, coatings, and/or substrates of the filament 120 over thelifetime usage of the microsensor 100. In examples, the adhesion coating180 is composed of any one or more of: a polyurethane, nafion, celluloseacetate, polyvinyl alcohol, polyvinyl butyrate, polyvinyl chloride,polydimethylsiloxane, paralyene, any material used in variations of theselective coating 170, and any other suitable adhesion material.However, in variations, a filament 120 of the microsensor 100 canalternatively not comprise an adhesion coating 180. Alternatively,layers, coatings, and/or substrates of the filament can be treated(e.g., heat treated, ultraviolet radiation treated, chemically bonded,etc.) and/or processed such that appropriate contact is maintained, evenwithout an adhesion coating 180.

As shown in FIG. 2F, any filament 120 can further comprise a temporaryfunctional layer 190, which functions to facilitate penetration of afilament 120 into the body. After the filament 120 has penetrated thebody, the temporary functional layer 190 is preferably configured todissolve or be absorbed by the body, leaving other portions of thefilament 120 to operate to detect target analytes/ions characterizing auser's body chemistry. The temporary functional layer 190 can beconfigured, such that the sensing layer 160 is at an appropriate depthfor detection (e.g., has access to interstitial fluid below the user'sstratum corneum), once the temporary functional layer 190 has penetratedthe user's body. The temporary functional layer 190 is preferablycomposed of an inert, bioabsorbable material that is porous; however,the temporary functional layer 190 can alternatively not be porous orbioabsorbable. In some variations, the temporary functional layer 190can be configured to release an initial ion concentration with a knownrelease profile (e.g., spiked or continuous release) in order tocalibrate the microsensor 100. In specific examples, the temporaryfunctional layer 190 can include a nitride material (e.g., 1000-2500 Åthick nitride), an oxide material, a carbide material, a salt, a sugar,a polymer (e.g., polyethylene glycol), and/or any other suitablematerial that does not deteriorate during subsequent processing steps.Other variations of the filament can further comprise any other suitabletemporary functional layer 190 providing any other suitable function.

Any filament 120 of the microsensor 100 can further comprise any otherappropriate functional layer or coating. In variations, a filament 120can comprise layers or coatings that perform any one or more of thefollowing functions: suppress or prevent an inflammatory response (e.g.,by comprising a surface treatment or an anti-inflammatory agent),prevent bio-rejection, prevent encapsulation (e.g., by comprising abio-inert substance, such as pyrolytic carbon), enhance targetanalyte/ion detection, and provide any other suitable anti-failuremechanism for the array of filaments 110. In one such variation, afilament 120 of the microsensor 100 can include a biocompatible layer185 appropriately situated (e.g., situated deeper than a temporaryfunctional layer 190, situated superficial to an adhesion layer, etc.)to enhance biocompatibility of the filament 120. In examples, thebiocompatible layer 185 can include a polymer (e.g., urethane, parylene,teflon, fluorinated polymer, etc.) or any other suitable biocompatiblematerial. In another variation, a filament 120 of the microsensor 100can additionally or alternatively include an intermediate protectivelayer 166 appropriately situated (e.g., situated deeper than a selectivelayer 170, etc.), which functions as an optional layer to provideintermediate protection and/or block transport of undesired species. Inexamples, the intermediate protective layer can include a polymer (e.g.,teflon, chlorinated polymer, nafion, polyethylene glycol, etc.) and caninclude functional compounds (e.g., lipids, charged chemical speciesthat block transport of charged species, etc.) configured to provide aprotective barrier. In another variation, a filament 120 of themicrosensor 100 can additionally or alternatively include a stabilizinglayer 163 appropriately situated (e.g., situated deeper than anintermediate protective layer 166, situated deeper than a selectivelayer 170, situated superficial to a sensing layer 160, etc.), whichfunctions to stabilize the sensing layer 160. In one example, thestabilizing layer 163 can include a polymer (e.g., electropolymerizedphenylenediamine) acting to stabilize a glucose-oxidase sensing layer160. In another variation, a filament 120 of the microsensor 100 canadditionally or alternatively include an intermediate selective layer145 appropriately situated (e.g., situated deeper than a sensing layer160, situated superficial to a conductive layer 140, etc.), whichfunctions to provide an additional selective layer. The intermediateselective layer can include or be coupled to an immobilizedcomplementary molecule (e.g., glucose oxidase) to facilitate analytedetection. In an example, the intermediate selective layer 145 includesa polymer (e.g., electropolymerized phenylenediamine) and is situatedsuperficial to a conductive layer 140; however, in variations of theexample, the intermediate selective layer 145 can include any othersuitable selective material and can be situated relative to other layersin any other suitable manner. In another variation, a filament 120 ofthe microsensor 100 can additionally or alternatively include anintermediate active layer 143 appropriately situated (e.g., situateddeeper than an intermediate selective layer 145, situated deeper than asensing layer 143, situated superficial to a conductive layer 140,etc.), which functions to facilitate transduction of a signal. As such,the intermediate active layer 143 can facilitate transduction invariations wherein the conductive layer 140 is not held at a givenpotential, and/or can facilitate transduction in any other suitablemanner. In one example, the intermediate active layer 143 comprises ironhexacyanoferrate (i.e., Prussian Blue) and in another example, theintermediate active layer 143 comprises nano-Platinum; however, theintermediate active layer 143 can additionally or alternatively includeany other suitable material.

In any of the above embodiments, variations, and examples, any one ormore of layers 185, 166, 163, 145, 143 can isolated to a desired regionof the filament 120, or can non-discriminately coat an entire surface ofthe filament 120 at a given depth. Furthermore, any filament 120 of themicrosensor 100 can include multiple instances of any layer or coating140, 143, 145, 150, 160, 163, 166, 170, 180, 185 190, can omit a layeror coating 140, 143, 145, 150, 160, 163, 166, 170, 180, 185 190, and/orcan include layers or coatings arranged in any other suitable mannerdifferent from the variations and examples described above and below. Inone such variation, a different configuration of layers can allowselective passage of molecules having different properties (e.g.,chemistries, size). However, any suitable configuration of a filament120 can be provided for any other suitable application.

As shown in FIG. 3 , each filament 120 of the array of filaments 110 canhave one of a variation of geometries. In a first geometric variation afilament 120 can be solid, examples of which are shown in FIGS. 3B and3D-3G. In a first example of the solid filament 120, the solid filament120 can have a profile tapering continuously to at least one point(e.g., pyramid or conical shaped with one or more pointed tips), and canhave straight or curved edges, as shown in FIGS. 3B, 3D, and 3G. Invariations, the point(s) of the filament 120 can be defined by anysuitable number of faces. In a second example of the solid filament 120,the solid filament 120 can comprise two regions—a pointed tip region 121configured to pierce a user's skin, and a blunt region 122 (e.g., acolumnar protrusion, a pillar), coupled to the pointed tip region, asshown in FIG. 3E. The pointed tip region 121 can be configured to bebioabsorbable, dissolve (e.g., using a degradable material) or, in anextreme example, break off (e.g., using an engineered stressconcentration) and be expelled from a user's system after the solidfilament 120 has penetrated the user's skin; however, the pointed tipregion 121 can alternatively be configured to remain attached to thesolid filament 120 after the solid filament 120 has penetrated theuser's skin. In a third example of the solid filament 120, the solidfilament 120 can comprise two regions—a barbed tip region 123 includinga barb configured to penetrate a user's skin and promote skin adherence,and a second region 122 coupled to the barbed tip region, as shown inFIG. 3F. In the third example of the solid filament 120, the barbed tipregion can be configured to have one sharp protrusion for skinpenetration, or can alternatively be configured to have multiple sharpprotrusions for skin penetration.

In a second geometric variation, examples of which are shown in FIGS.3A, 3C, and 3H, a filament 120 can be hollow and comprise a channel 125within an interior region of the hollow filament 120. In a first exampleof the hollow filament 120, the hollow filament 120 can have a profiletapering continuously to at least one point (e.g., pyramid or conicalshaped with one or more pointed tips), and can have straight or curvededges. Furthermore, the point(s) of the filament 120 can be defined byany suitable number of faces. In the first example of the hollowfilament 120, the hollow filament 120 can additionally be processed tohave one or more channels 125 configured to facilitate sensing of ananalyte characterize a user's body chemistry. In the first example, achannel 125 of the hollow filament 120 can be characterized by a uniformcross section along the length of the channel 125, or can alternativelybe characterized by a non-uniform cross section along the length of thechannel 125. In a second example of a hollow filament 120, the hollowfilament 120 can be configured to receive a volume of the user's bodyfluid into a sensing chamber to facilitate analyte detection. In thesecond geometric variation, the hollow filament 120 can be composed of ametal or a semiconductor, or any appropriate material to facilitateanalyte sensing. In other examples, the hollow filament 120 mayimplement a variation of any of the solid filaments described above, butbe processed to have at least one channel 125 within an interior regionof the hollow filament 120. Each filament 120 in the array of filaments110 can include a combination of any of the above geometric variations,a different variation of the above geometric variations, andfurthermore, the array of filaments 110 can comprise filamentscharacterized by different geometric variations.

In a first specific example of a filament 120, as shown in FIG. 2A, asolid filament 120 comprises a uniform silicon substrate 130 composed toP-type, boron-doped orientation <100> silicon with a resistivity from0.005-0.01 ohm-cm, a thickness of 500-1500 μm, and a TTV less than 10μm, processed to define a substrate core with a pointed tip region 121formed by way of a dicing saw, as described in Section 2 below. In thefirst specific example, the filament comprises a conductive layer 140 ofnickel, coupled to the substrate 130 by electroplating, wherein theconductive layer 140 is isolated to the pointed tip region 121 of thesubstrate core, and to a face of the substrate 130 directly opposing theface including the filament 120. In the first specific example, thefilament 120 further includes an insulating layer 150 of 1 μm oxide,formed by thermal growth at 900-1050 C for 1-2 hours, as described infurther detail below, wherein the insulating layer 150 is formed at allexposed surfaces of the substrate 130 and defines an active region atthe pointed tip region 121 of the filament 120. In variations of thefirst specific example, the conductive layer 140 can additionally oralternatively include one or more of a gold-based material and aplatinum-based material. Furthermore, in the first specific example, thefilament 120 can include a conductive polymer (polypyrrole) coating asthe sensing layer 160 coupled to the conductive layer 140 at the pointedtip region 121 of the filament 120, and a PVC selective coating 170 withcomplementary molecules 171 to target analytes coupled to the sensinglayer 160. In the first specific example, the solid filament 120 isincludes a rectangular prismatic columnar protrusion, with a pointed tipregion defined by four faces tapering to a point, as shown in FIG. 5C,wherein two of the four faces are orthogonal to each other andcontiguous with two faces of the rectangular prismatic columnarprotrusion, and wherein the other two faces are formed by way of adicing saw with an angled blade, as described further in Section 2below.

In a second specific example of a filament 120 for glucose sensing,which can be characterized as shown in FIG. 2B, a solid filament 120comprises a uniform silicon substrate 130 composed to P-type,boron-doped orientation <100> silicon with a resistivity from 0.005-0.01ohm-cm, a thickness of 500-1500 μm, and a TTV less than 10 μm, processedto define a substrate core with a pointed tip region 121 formed by wayof a dicing saw, as described in Section 2 below. In the second specificexample, the filament comprises a conductive layer 140 of nickel, gold,and platinum, coupled to the substrate 130 by electroplating, whereinthe conductive layer 140 is isolated to the pointed tip region 121 ofthe substrate core, and to a face of the substrate 130 directly opposingthe face including the filament 120. In the second specific example, thefilament 120 further includes an insulating layer 150 of 0.1-10 μmoxide, formed by thermal growth at 900-1050 C for 1-2 hours, asdescribed in further detail below, wherein the insulating layer 150 isformed at all exposed surfaces of the substrate 130 and defines anactive region including the conductive layer 140 at the pointed tipregion 121 of the filament 120. Furthermore, in the second specificexample, the filament includes electropolymerized phenylenediamene,tyramine, glucose oxidase, and poly-lysine as the sensing layer 160superficial to the conductive layer 140 at the pointed tip region 121 ofthe filament 120. In between the conductive layer 140 and the sensinglayer 160 at the pointed tip region 121, the second specific exampleincludes an intermediate selective layer 145 of electropolymerizedphenylenediamine polymer coupled to an intermediate active layer 143including iron hexacyanoferrate, coupled directly to the conductivelayer 140. Finally the second specific example includes an intermediateprotective layer 166 of urethane, coupled to a stabilizing layer 163 ofphenylenediamine coupled to the sensing layer 160, surrounded by a PVCselective coating 170 with complementary molecules 171 to targetanalytes coupled to the sensing layer 160. In the second specificexample, the solid filament 120 is includes a rectangular prismaticcolumnar protrusion, with a pointed tip region defined by four facestapering to a point, as shown in FIG. 5C, wherein two of the four facesare orthogonal to each other and contiguous with two faces of therectangular prismatic columnar protrusion, and wherein the other twofaces are formed by way of a dicing saw with an angled blade, asdescribed further in Section 2 below.

In a third specific example of a filament 120, as shown in FIG. 2C, asolid filament 120 comprises a uniform silicon substrate 130, aconductive layer 140 of platinum at the tip of the filament 120, aninsulating layer 150 composed of polyimide isolating the active regionof the filament 120 to the tip of the filament, a conductive polymer(polypyrrole) coating as the sensing layer 160, and a PVC selectivecoating 170 with complementary molecules 171 to target analytes. In thethird specific example, the solid filament 120 is conical and has aprofile tapering to a single sharp point.

In a fourth specific example of a filament 120, as shown in FIG. 2D, ahollow filament 120 comprises a uniform silicon substrate 130, anexternal surface coated with an insulating layer 150 composed ofpolyimide, a conductive layer 140 of platinum covering the surface of aninterior channel 125, a conductive polymer (polypyrrole) coating as asensing layer 160 covering the conductive layer 140 of platinum, and aselective PVC coating 170 covering the sensing layer 160. In the fourthspecific example, the hollow filament 120 is conical with a singlecylindrical channel 125 passing through the axis of rotation of theconical filament 120.

Each filament 120 in the array of filaments 110 can also be structuredas any appropriate combination of the above variations and/or examplesof filament 120 composition and/or geometry, and/or can be paired with afilament 120 serving as a reference electrode configured to normalize asignal detected in response to analyte sensing. Additionally, the arrayof filaments 110 can comprise filaments characterized by differentvariations of filament composition (e.g., composition of layers and/orcoatings).

2. Manufacturing Method

As shown in FIG. 4 , an embodiment of a manufacturing method 200 for themicrosensor comprises forming a filament substrate S210; applying aconductive layer to the filament substrate S220; defining an activeregion and a non-active region of the filament with an insulating layerS230; applying a sensing layer to at least the conductive layer S240;and forming a selective layer S250, coupled to the sensing layer,configured to target at least one specific analyte characterizing bodychemistry. The manufacturing method 200 functions to form an array offilaments as part of a microsensor for monitoring body chemistry.Preferably, the manufacturing method 200 forms an array of substantiallyidentical filaments, wherein each filament in the array of filamentscomprises an active region for analyte detection, and a non-activeregion comprising an insulating layer. Alternatively, the manufacturingmethod 200 can form an array of substantially non-identical filaments,with different portions of the array having different functionalitiesand/or configurations.

2.1 Manufacturing Method—Substrate, Conductive Layer, and InsulatingLayer Processing

Block S210 recites forming a filament substrate, and functions to form acore or base structure upon which other layers or coatings can beapplied, in order to facilitate processing of each filament for specificfunctionalities. As shown in FIG. 5A, in a first variation, Block S210includes forming an array of protrusions at a first surface of thesubstrate, byway of a dicing saw S211. In variations of Block S211,forming an array of protrusions can include forming an array of sharpprotrusions S211 a, as shown in FIGS. 5B and 5C, by way of an angledblade (e.g., a 60 degree blade, a 45 degree blade) of a dicing saw orother saw characterized by a desired depth (e.g., 150-500 μm),configured to cut a desired number of facet-filament tips (e.g., 2-facettips, 4-facet tips, 6-facet tips, etc.) at a desired rate (e.g., 1-10mm/s). In block S211 a, the dicing saw can be configured to form thearray of sharp protrusions through adjacent cuts in a first direction,followed by adjacent cuts in a second direction (e.g., orthogonal to thefirst direction), thereby forming a 2-dimensional array of sharpprotrusions (i.e., sharp tips). However, any suitable number of cuts inany suitable number of directions can be used to form the array.Additionally or alternatively, forming the array of protrusions in BlockS211 can including forming an array of columnar protrusions S211 b atthe first surface of the substrate, by way of a non-angled blade of adicing saw of a desired depth (e.g., 25-500 μm) and width (e.g., 75-200μm) with a desired gap (e.g., 25-20000 μm), configured to cut a desirednumber of columnar protrusions at a desired rate (e.g., 1-10 mm/s),wherein each columnar protrusion defines any suitable cross sectionalprofile (e.g., polygonal, non-polygonal). In block S211 b, the dicingsaw can be configured to form the array of columnar protrusions throughadjacent cuts in a first direction, followed by adjacent cuts in asecond direction (e.g., orthogonal to the first direction), therebyforming a 2-dimensional array of columnar protrusions. However, anysuitable number of cuts in any suitable number of directions can be usedto form the array.

In variations of Block S211, Blocks S211 a and S211 b preferably formprotrusions with a sharp tip defined at the end of each columnarprotrusion in a one-to-one manner, as shown in FIG. 5B, wherein thesharp tip is substantially aligned with and contiguous with a respectivecolumnar protrusion: however, the sharp tip(s) can be non-aligned with arespective columnar protrusion, can be non-contiguous with a respectivecolumnar protrusion, and/or can be formed in a non-one-to-one mannerwith the array of columnar protrusions. In some variations, a sharp tipcan comprise a pyramidal tip region defined by an irregular pyramid,having a first pair of orthogonal faces, substantially contiguous withtwo faces of the columnar protrusion, and a second pair of orthogonalfaces, angled relative to the first pair of orthogonal faces, such thatthe tip is substantially aligned with a vertex of the rectangular crosssection of the columnar protrusion; however, in other variations, thetip can be misaligned with a vertex of the rectangular cross section ofthe columnar protrusion. Furthermore, Blocks S211 a and S211 b can beperformed in any suitable order, in order to facilitate application ofthe conductive layer to the filament substrate in variations of BlockS220 and/or defining an active region and a non-active region of thefilament with an insulating layer, in variations of Block S230. In stillfurther variations, alternatives to the first variation of Block S210can include forming the array of protrusions at the first surface of thesubstrate by way of any other suitable method of bulk material removal.

In the first variation, the substrate can be composed of asemiconducting material (e.g., silicon, quartz, gallium arsenide), aconducting material (e.g., gold, steel, platinum), and/or an insulatingmaterial (e.g., glass, ceramic). In some variations, the substrate 130can comprise a combination of materials (e.g., as in a composite, as inan alloy). In a specific example, the substrate is composed of P-type,boron-doped, <100> orientation silicon with a resistivity of 0.005-0.01ohm-cm, a thickness from 500-1500 μm, and a TTV of <10 μm, with a firstsurface side polish. In variations of the specific example, thesubstrate 130 can be composed of silicon with any other suitable type,doping, miller index orientation, resistivity, thickness, TTV, and/orpolish.

As shown in FIG. 6A, in a second variation, Block S210 comprisescreating a substrate, applying a photoresist to the substrate, andetching the substrate to form the filament substrate. The secondvariation of Block S210 preferably defines an array of sharpprotrusions, wherein each sharp protrusion has a base end, coupled tothe substrate, a sharp tip end, and a rotational axis of symmetrydefined between the base end and the sharp tip end. In variations, eachsharp protrusion can be defined by an inwardly tapering profile, suchthat sharp protrusion has a base end defined by a first width (ordiameter), and widens from the base end for at least a portion of thelength of the sharp protrusion. However, the second variation of BlockS210 can include forming protrusions, defined by any other suitableprofile, at the substrate. The second variation can comprise performinga Bosch process, a deep-reactive ion etching (DRIE) process, anysuitable etch (e.g., a potassium hydroxide etch), or any other suitableprocess to form the filament substrate. In a specific example of thesecond variation, the substrate comprises a P++ and/or silicon-dopedsilicon wafer with an oxide pad, a negative photoresist is applied in auniform pattern to the oxide pad, and potassium hydroxide anisotropicetching is used to form the filament substrate. In further detailregarding the specific example, the substrate is composed of P-type,boron-doped, <100> orientation silicon with a resistivity of 0.005-0.01ohm-cm, a thickness from 500-1500 μm, and a TTV of <10 μm, with a firstsurface side polish. In variations of the specific example, thesubstrate 130 can be composed of silicon with any other suitable type,doping, miller index orientation, resistivity, thickness, TTV, and/orpolish. In alternative examples of the second variation, Block S210 cancomprise using any appropriate semiconductor substrate, applying apositive photoresist and/or a negative photoresist to the semiconductorsubstrate, applying the photoresist in a non-uniform pattern, and/orusing any appropriate etching method (e.g., anisotropic, isotropic) toform the filament substrate.

In a third variation, as shown in FIG. 6B, Block S210′ comprises etchingan array into a ductile substrate and deforming the array to form anarray of protrusions, thus forming a filament substrate. In a specificexample of the third variation, an array of v-shaped features islaser-etched into a ductile steel substrate, and each v-shaped featurein the array of v-shaped features is then deformed outward from thesteel substrate by 90° to form an array of v-shaped filamentprotrusions. Alternative examples of the third variation can includeetching the array using any appropriate method (e.g., punching,die-cutting, water cutting), etching any appropriate array feature(e.g., any pointed feature), and deforming the array in any appropriatemanner (e.g., by any angular amount for each or all array features) toform the array of protrusions. In alternative variations, the filamentsubstrate can be formed by any other suitable method (e.g., molding,laser cutting, stamping, 3D printing, etc.).

Block S220 recites applying a conductive layer to the filament substrateS220, and functions to form a conductive “active” region to facilitatesignal transmission upon detection of an analyte by a filament of themicrosensor. Preferably, Block S220 comprises coupling a conductivelayer to the sharp tip of each columnar protrusion in the array ofcolumnar protrusions formed, for example, in variations of Block S211 aand S211 b. In variations, coupling the conductive layer can includeelectroplating a conductive material or alloy of a conductive material(e.g., nickel, silver, iridium, tungsten, titanium, titanium nitride,aluminum, cadmium, chromium, molybdenum, lead, gold, platinum, etc.) tothe sharp tip of each columnar protrusion. Block S220 can additionallyor alternatively comprise metalizing the filament substrate bysputtering a layer of any appropriate conductive material (e.g., gold,platinum, doped silicon, nickel, silver, iridium, tungsten, titanium,titanium nitride, aluminum, cadmium, chromium, molybdenum, lead, etc.)onto the filament substrate. In still other variations, however, BlockS220 can alternatively or additionally comprise metalizing the filamentsubstrate by plating or evaporating a layer of any appropriateconductive material onto the filament substrate, or by applying theconductive material (e.g., nickel, gold, platinum, doped silicon,tungsten, iridium, titanium nitride) in any other suitable manner. Inaddition to applying the conductive material to the sharp tips of thearray of protrusions defined in Block S210, Block S220 can includecoupling a second conductive layer to a second surface of the substrate(e.g., a surface of the substrate directly opposing the array ofprotrusions), in order to define a second conductive surface of thesubstrate to facilitate electrical coupling for signal transmission(e.g., upon detection of an analyte).

Preferably, Block S220 comprises applying the conductive layer to thefilament substrate in a substantially uniform manner (e.g., as an evenlayer with substantially uniform thickness); however, Block S220 canalternatively comprise applying the conductive layer to the filamentsubstrate in a non-uniform manner, such that some regions of theconductive layer are thicker than others. Furthermore, Block S220 caninclude application of multiple layers of one or more conductivematerials, in order to form a conductive layer comprising multiplelayers of materials. In variations involving sputtering or evaporation,the filament substrate can be translated or rotated while being sputtercoated or evaporation coated to facilitate uniform deposition of theconductive layer. In variations involving plating to apply theconductive layer, the plating can be applied using chemical orelectrochemical plating, to any appropriate thickness.

Block S230 recites defining an active region and a non-active region ofthe filament with an insulating layer, and functions to form at leastone insulating region of a filament of the microsensor. Preferably,Block S230 comprises applying an insulating layer to a portion of thefilament substrate/conductive layer assembly, in a manner wherein atleast one region of the conductive layer is not covered (e.g.,uncovered, exposed, unsheathed) with the insulating layer (thus formingthe active and non-active regions of the filament). Block S230 can beperformed using thermal oxide growth, spin coating, spray coating, orany other appropriate method of depositing a localized layer of aninsulting material. Preferably, the insulating layer is composed of aninsulating oxide; however, the insulating layer can additionally oralternatively include an insulating polymer (e.g., polyimide, cyanateester) that is chemical and heat resistant and/or any appropriatematerial (e.g., thermally grown silicon oxide, chemical vapor depositedoxides, titanium oxide, tantalum oxide, other oxides, chemical vapordeposited nitrides, other nitrides, paralene, etc.) that is configuredto insulate a portion of the filament substrate/conductive layerassembly. Furthermore, in Block S230, the insulating layer can be grownor deposited uniformly or non-uniformly over desired surfaces (e.g., allexposed surfaces, active regions formed through bulk material removal,active regions defined by chemical etching, plasma etching, high energyetching, any other suitable type of etching, etc.).

In a first example of Block S230, an oxide layer can be formed atexposed surfaces of the substrate (e.g., all exposed surfaces of thesubstrate, of substrate cores of protrusions, cut surfaces, etc.), by athermal oxide growth process. The oxide layer preferably couples to theexposed surfaces of the substrate in a manner that discourages unbondingor removal of the oxide material during subsequent Blocks of the method200. In the first example, the oxide layer is formed by way of a thermaloxide growth process at 900-1050 C for 1-2 hours, in order to induce0.1-10 μm thick thermal oxide growth. In variations of the firstexample, however, the oxide layer can be formed at the substrate orcoupled to the substrate using a thermal process defined by any suitabletemperature parameters, for any suitable duration of time, in order todefine an oxide layer of any other suitable thickness.

In a second example of Block S230′, as shown in FIG. 7A, an insulatingpolymer (e.g., polyimide, cyanate ester) can be deposited over thesubstrate or substrate/conductive layer subassembly S231. The insulatormay then be soft-baked S232 to facilitate selective removal of theinsulating polymer. In the second example, the tip regions of thefilaments can then be exposed by selectively dissolving or etching thesoft-baked insulating polymer S233, and the tip regions of the filamentscan be cleaned S234 (e.g., using a plasma-etching process). Finally, thefilament assembly comprising active and non-active regions can behard-baked to cure the insulating polymer S235. In a variation of thesecond example, the insulating polymer can be photosensitive, such thatBlock S232 uses a photolithographic process to selectively expose areasabove filaments or between filaments (to increase solubility), and sothat the a positive photolithographic process or a negativephotolithographic process can be used to define the active/non-activeregions. Additionally, Block S235 can use a photo-crosslinking processto cure the insulating polymer.

In a third example of Block S230″, as shown in FIG. 7B, a set of oxidecaps coupled to filament tips (produced, for instance, during a Bosch orDRIE process) can be used to shield the filament tips S236, and adielectric or other insulating material can be applied to define activeand non-active regions S237. The insulating material in the thirdexample can be applied using a line of sight deposition method,preferably at an angle, such that the insulating material is appliedonly to specific regions (e.g., between filament tips). The line ofsight deposition method can be an evaporation method (e.g., to depositan insulating polymer), or can additionally or alternatively be asputtering method (e.g., sputtering of titanium or tantalum), followedby oxidation to produce the insulating layer. The filament assembly canthen be passivated (e.g., during a DRIE process) and the oxide caps canbe removed (e.g., pinched off) to expose the active regions.

In a fourth example of Block S230′″, as shown in FIG. 7C, the insulatingmaterial can be fluidly deposited between filament structures (e.g., byinkjet printing, silk screening, dispensing) S238. The insulatingmaterial can be a molten polymer (e.g., nylon), or can be a polymer thatis in solution form (e.g., silicon, polyurethane, polyimide) that issubsequently cured S235′ (e.g., baking, photo-crosslinking) to removesolvent and form the active and non-active regions.

In a fifth example of Block S230″″, as shown in FIG. 7D, a photoresistcan be applied to the substrate or substrate/conductive layersubassembly S239, and then etched away to expose filament tips S271. Thetips may then be protected with a intermediary layer (e.g., metal orsoluble insulator) S272, the photoresist can be removed by furtheretching S273, and then non-tip regions may then be passivated to formnon-active insulating regions S274. Finally, the intermediary layer canbe removed to define the active regions S275. Block S230 canalternatively comprise any other suitable method of defining an activeregion and a non-active region of the filament with an insulating layer.

In a sixth example of Block S230′″″, the insulating material (e.g.,parylene) used to define the active regions and non-active regions canalso be deposited by a chemical vapor deposition (CVD) process. In thisexample, the tips of the filaments can be protected with a temporaryprotective layer (e.g., by covering each needle tipphotolithographically using photoresist or applying a small droplet ofphotoresist or other soluble polymer to each filament tip). Then, theinsulating material (e.g., parylene) can be deposited in a CVD processto conformally coat the unprotected filament areas. After deposition ofthe insulating material, the temporary protective layer can be removed(e.g., by using an appropriate solvent), to form the active and thenon-active regions.

In variations of the method 200, Blocks S220 and S230 can be performedin any suitable order, in relation to defining an array of sharp tips invariations of Block S210, and in order to define active/non-activeregions. In a first variation of the method 200, forming an array ofcolumnar protrusions S211 b at the substrate can be performed prior toforming an insulating layer at exposed surfaces of the substrate inBlock S230. Then, the insulating layer can be selectively removed, asdesired, from surfaces of the substrate (e.g., at a surface of thesubstrate directly opposing that of the array of columnar protrusions).After selective removal of the insulating layer, an array of sharpprotrusions can be formed at distal ends of the array of columnarprotrusions in variations of the method including Block S211 a, and theconductive layer can be coupled to all regions of the substrate notcovered by the insulating layer, thereby coupling the conductive layerto at least the tip regions of the array of protrusions in a variationof Block S220. As such, active region/non-active regions can be definedthrough bulk material removal (e.g., cutting, dicing) or any othersuitable process including one or more of: selective chemical etching,plasma etching, high energy etching, and any other suitable etchingmethod.

In a second variation, which can extend from the first variation, themethod 200 can include Blocks S210, S220, and S230, and further includeusing a sacrificial layer to selectively isolate a region of thesubstrate during processing S283, in order to facilitate processing ofthe conductive layer and/or the insulating layer in Blocks S220 andS230, respectively. The sacrificial layer can include a nitride material(e.g., 1000-2500 Å thick nitride), an oxide material, a carbidematerial, a salt, a sugar, a polymer (e.g., polyethylene glycol), and/orany other suitable material that does not deteriorate during subsequentprocessing steps. Furthermore, the sacrificial layer can bebioabsorbable and/or porous to facilitate biocompatibility and/orprocessing. In one example, forming an array of sharp protrusions S211 acan be performed prior to coupling a conductive layer to the array ofsharp protrusions and any other desired surface of the substrate (e.g.,a surface directly opposing that of the array of sharp protrusions), asin variations of Block S230, followed by coupling of a sacrificial layerto all surfaces of the substrate with the conductive layer. In thisexample, an array of columnar protrusions can be formed as in Block S211b by removing material between the array of sharp protrusions, afterwhich an insulating layer can be generated at all exposed surfaces ofthe substrate, as in Block S230. The sacrificial layer can then beremoved prior to subsequent processing steps. In another example,forming an array of sharp protrusions S211 a can be performed prior tocoupling of a sacrificial layer, as in Block S283, at all surfaces ofthe substrate intended to be coupled to a conductive layer. Material canthen be removed between the array of sharp protrusions to form an arrayof columnar protrusions, as in Block S211 b, after which an insulatinglayer can be formed at all exposed surfaces of the substrate, as inBlock S230. Then, the sacrificial layer can be removed and theconductive layer can be coupled to all regions of the substrate formerlyoccupied by the sacrificial layer, as in variations of Block S220. Inother examples, coupling of the sacrificial layer can be omitted orperformed at any suitable stage of the method 200, specific examples ofwhich are described in further detail below.

As shown in FIG. 8A, in a first specific example of processing thesubstrate, the conductive layer, and the sensing layer in Blocks S210,S220, and S230, material is removed from a first surface of thesubstrate, thereby forming an array of columnar protrusions as in BlockS211 b. Removing material in the first specific example is performed byway of a non-angled blade of a dicing saw in order to remove materialfrom the first surface of the substrate to a desired depth of 400 μm, awidth of 100 μm, and a gap of 500 μm, at a cutting rate of 2-3 mm/s. Inthe first specific example, the dicing saw is configured to form thearray of columnar protrusions through adjacent cuts in a firstdirection, followed by adjacent cuts in a second direction orthogonal tothe first direction, thereby forming a 2-dimensional array of columnarprotrusions. In the first specific example, the substrate is composed ofP-type, boron-doped, <100> orientation silicon with a resistivity of0.005-0.01 ohm-cm, a thickness from 500-1500 μm, a total thicknessvariation (TTV) of <10 μm, and with a first surface side polish.Subsequent to formation of the array of columnar protrusions, aninsulating layer of ˜1 μm oxide is formed at all exposed surfaces of thesubstrate, as in Block S240, by inducing thermal oxide growth at900-1050 C for 1-2 hours. Then, the insulating layer is removed from asecond surface of the substrate, directly opposing the surface of thesubstrate at which the columnar protrusions were formed, by way of adirected plasma etch. Subsequently, an array of sharp protrusions isformed, as in Block S211 a, by removing material from the distal end ofeach columnar protrusion. Forming an array of sharp protrusions isperformed by way of a 500 μm, 60-degree angled blade of a dicing sawconfigured to cut 2-facet tips at a rate of 4 mm/s. Similar to formingthe array of columnar protrusions, the dicing saw is configured to formthe array of sharp protrusions through adjacent cuts in a firstdirection, followed by adjacent cuts in a second direction orthogonal tothe first direction, thereby forming a 2-dimensional array of sharpprotrusions (i.e., sharp tips). Lastly, in the first specific example, aconductive layer is coupled to the array of sharp protrusions and thesecond surface of the substrate by electroplating (e.g., of nickel, ofgold, and/or of platinum), as in Block S220.

As shown in FIG. 8B, in a second specific example of processing thesubstrate, the conductive layer, and the sensing layer in Blocks S210,S220, and S230, material is removed from a first surface of thesubstrate, thereby forming an array of columnar protrusions as in BlockS211 b. Removing material in the second specific example is performed byway of a non-angled blade of a dicing saw in order to remove materialfrom the first surface of the substrate to a desired depth of μ400 μm, awidth of 100 μm, and a gap of 500 μm, at a cutting rate of 2-3 mm/s. Inthe second specific example, the dicing saw is configured to form thearray of columnar protrusions through adjacent cuts in a firstdirection, followed by adjacent cuts in a second direction orthogonal tothe first direction, thereby forming a 2-dimensional array of columnarprotrusions. In the second specific example, the substrate is composedof P-type, boron-doped, <100> orientation silicon with a resistivity of0.005-0.01 ohm-cm, a thickness from 500-1500 μm, a total thicknessvariation (TTV) of <10 μm, and with a first surface side polish.Subsequent to formation of the array of columnar protrusions, aninsulating layer of ˜1 μm oxide is formed at all exposed surfaces of thesubstrate, as in Block S230, by inducing thermal oxide growth at900-1050 C for 1-2 hours. Then, the insulating layer is removed from asecond surface of the substrate, directly opposing the surface of thesubstrate at which the columnar protrusions were formed, by way of adirected plasma etch. Following removal of the insulating layer from thesecond surface, a sacrificial layer is coupled to all surfaces of thesubstrate still coupled to the insulating layer. Subsequently, an arrayof sharp protrusions is formed, as in Block S211 a, by removing materialfrom the distal end of each columnar protrusion. Forming an array ofsharp protrusions is performed by way of a 500 μm, 60-degree angledblade of a dicing saw configured to cut 2-facet tips at a rate of 4mm/s. Similar to forming the array of columnar protrusions, the dicingsaw is configured to form the array of sharp protrusions throughadjacent cuts in a first direction, followed by adjacent cuts in asecond direction orthogonal to the first direction, thereby forming a2-dimensional array of sharp protrusions (i.e., sharp tips). Lastly, inthe second specific example, a conductive layer is coupled to the arrayof sharp protrusions and the second surface of the substrate byelectroplating (e.g., of nickel, of gold, and/or of platinum) as inBlock S220, followed by removal of the sacrificial layer from theinsulating layer. The sacrificial layer, in the second specific example,thus functions to facilitate isolation of the conductive layer todesired surfaces, such that the conductive layer does not substantiallyoverlap with the insulating layer in an undesired manner.

As shown in FIG. 8C, in a third specific example of processing thesubstrate, the conductive layer, and the sensing layer in Blocks S210,S220, and S230, material is removed from a first surface of thesubstrate to form an array of sharp protrusions (e.g., sharp tips), asin Block S211 a. Forming an array of sharp protrusions is performed byway of a 500 μm, 60-degree angled blade of a dicing saw configured tocut 2-facet tips at a rate of 4 mm/s. In the third specific example, thedicing saw is configured to form the array of sharp protrusions throughadjacent cuts in a first direction, followed by adjacent cuts in asecond direction orthogonal to the first direction, thereby forming a2-dimensional array of sharp protrusions. In the third specific example,the substrate is composed of P-type, boron-doped, <100> orientationsilicon with a resistivity of 0.005-0.01 ohm-cm, a thickness from500-1500 μm, a total thickness variation (TTV) of <10 μm, and with afirst surface side polish. Subsequent to forming the array of sharpprotrusions, a conductive layer is coupled to the array of sharpprotrusions and a second surface of the substrate, directly opposed tothe array of sharp protrusions, as in Block S220, by depositing 1000 Åof platinum, 1000 Å of iridium, 1000 Å of tungsten, and 100 Å oftitanium nitride at the desired surfaces. In variations of the thirdspecific example, the conductive layer can include: a 1000 Å thickplatinum layer and a 100 Å thick titanium layer, a 1000 Å thick platinumlayer and a 100 Å thick titanium nitride layer, a 1000 Å thick iridiumlayer and a 100 Å thick titanium nitride layer, or a 1000 Å thicktungsten layer. A sacrificial layer comprising a 1000-2500 Å thick layerof nitride is then coupled to the conductive layer, as in Block S283,and material is removed from the substrate between each sharp protrusionin the array of sharp protrusions, thereby forming an array of columnarprotrusions coupled to the array of sharp protrusions, as in Block S211b. Forming the array of columnar protrusions is performed by way of anon-angled blade of a dicing saw in order to remove material from thefirst surface of the substrate to a desired depth of 400 μm, a width of100 μm, and a gap of 500 μm, at a cutting rate of 2-3 mm/s. In the thirdspecific example, the dicing saw is configured to form the array ofcolumnar protrusions through adjacent cuts in a first direction,followed by adjacent cuts in a second direction orthogonal to the firstdirection, thereby forming a 2-dimensional array of columnarprotrusions. An insulating layer is formed at all exposed surfaces(e.g., cut surfaces without conductive layer or sacrificial layer) ofthe substrate, as in Block S230, by inducing thermal oxide growth to athickness of 10 μm at 900-1050 C for 1-2 hours. Then, the sacrificiallayer is removed by a directed plasma etch.

As shown in FIG. 8D, in a fourth specific example of processing thesubstrate, the conductive layer, and the sensing layer in Blocks S210,S220, and S230, material is removed from a first surface of thesubstrate to form an array of sharp protrusions (e.g., sharp tips), asin Block S211 a. Forming an array of sharp protrusions is performed byway of a 500 μm, 60-degree angled blade of a dicing saw configured tocut 2-facet tips at a rate of 4 mm/s. In the fourth specific example,the dicing saw is configured to form the array of sharp protrusionsthrough adjacent cuts in a first direction, followed by adjacent cuts ina second direction orthogonal to the first direction, thereby forming a2-dimensional array of sharp protrusions. In the fourth specificexample, the substrate is composed of P-type, boron-doped, <100>orientation silicon with a resistivity of 0.005-0.01 ohm-cm, a thicknessfrom 500-1500 μm, a total thickness variation (TTV) of <10 μm, and witha first surface side polish. A sacrificial layer comprising a 1000-2500Å thick layer of nitride is then coupled to the array of sharpprotrusions and to a second surface of the substrate directly opposingthe array of sharp protrusions, as in Block S283, and material isremoved from the substrate between each sharp protrusion in the array ofsharp protrusions, thereby forming an array of columnar protrusionscoupled to the array of sharp protrusions, as in Block S211 b. Formingthe array of columnar protrusions is performed by way of a non-angledblade of a dicing saw in order to remove material from the first surfaceof the substrate to a desired depth of μ400 μm, a width of 100 μm, and agap of 500 μm, at a cutting rate of 2-3 mm/s. In the fourth specificexample, the dicing saw is configured to form the array of columnarprotrusions through adjacent cuts in a first direction, followed byadjacent cuts in a second direction orthogonal to the first direction,thereby forming a 2-dimensional array of columnar protrusions. Aninsulating layer is formed at all exposed surfaces (e.g., cut surfaceswithout sacrificial layer) of the substrate, as in Block S230, byinducing thermal oxide growth to a thickness of 1 μm at 900-1050 C for1-2 hours. Then, the sacrificial layer is removed by a directed plasmaetch. Subsequent to removal of the sacrificial layer, a conductive layeris coupled to the array of sharp protrusions and a second surface of thesubstrate, directly opposed to the array of sharp protrusions, as inBlock S220, by depositing 1000 Å of platinum, 1000 Å of iridium, 1000 Åof tungsten, and 100 Å of titanium nitride at the desired surfaces. Invariations of the fourth specific example, the conductive layer caninclude: a 1000 Å thick platinum layer and a 100 Å thick titanium layer,a 1000 Å thick platinum layer and a 100 Å thick titanium nitride layer,a 1000 Å thick iridium layer and a 100 Å thick titanium nitride layer,or a 1000 Å thick tungsten layer. Other variations of the fourthspecific example can include electroplating of any suitable metal (e.g.,nickel, gold, platinum).

As shown in FIG. 8E, in a fifth specific example of processing thesubstrate, the conductive layer, and the sensing layer in Blocks S210,S220, and S230, an array of sharp protrusions, with a tapered profile(i.e., tapering from a tip end toward a base end coupled to thesubstrate), is formed at a first surface of a substrate by a DRIEprocess, as in Block S210. A conductive layer is then coupled to allexposed surfaces of the substrate, as in Block S220 by depositing 1000 Åof platinum, 1000 Å of iridium, 1000 Å of tungsten, and 100 Å oftitanium nitride at the exposed surfaces. In variations of the fifthspecific example, the conductive layer can include: a 1000 Å thickplatinum layer and a 100 Å thick titanium layer, a 1000 Å thick platinumlayer and a 100 Å thick titanium nitride layer, a 1000 Å thick iridiumlayer and a 100 Å thick titanium nitride layer, or a 1000 Å thicktungsten layer. Other variations of the fifth specific example caninclude electroplating of any suitable metal (e.g., nickel, gold,platinum) to form the conductive layer. Subsequent to formation of theconductive layer, an insulating layer comprising a nitride material isthen coupled to the conductive layer, as in Block S230, and asacrificial layer is then coupled to the insulating layer, as in BlockS283, at regions of the substrate between the base ends of the array ofsharp protrusions. In the fifth specific example, the sacrificial layeris applied by way of a spin photoresist. Subsequently, the insulatinglayer is removed from the tip regions of the array of sharp protrusionsand from a second surface of the substrate, directly opposed to thearray of sharp protrusions, by way of an anisotropically directed plasmafield. Lastly, the sacrificial layer is removed (e.g., by etching).

In other examples of the method 200, processing the substrate, theconductive layer, and the sensing layer in Blocks S210, S220, and S230can be performed according to any other suitable process and in anyother suitable order. Furthermore, in variations of the describedprocesses, any suitable number of blades, cutting surfaces, other toolfor removal of material can be used to increase processingspeed/efficiency.

2.2 Manufacturing Method—Sensing Layer and Selective Layer Processing

Block S240 recites applying a sensing layer to at least the conductivelayer, and functions to form a filament coating that enablestransduction of an ionic concentration to an electronic voltage.Preferably, the sensing layer is applied selectively to the filamentsubstrate/conductive layer/insulating layer assembly at regions wherethe conductive layer is exposed (e.g., only at active regions); however,the sensing layer can alternatively be applied to the entire filamentsubstrate/conductive layer/insulating layer assembly. In variationswherein the sensing layer is applied selectively to the filamentsubstrate/conductive layer/insulating layer assembly, Block S240 cancomprise electrodeposition, lithography, inkjet printing, screenprinting, or any other appropriate method for applying the sensing layerselectively. In variations wherein the sensing layer is applied to theentire filament substrate/conductive layer/insulating layer assembly,Block S240 can comprise glazing, spin coating, spray coating, or anymethod of applying a polymer coating in a non-selective manner.Preferably, the sensing layer is composed of a material with reversibleredox reaction behavior, as previously described. In one example, thesensing layer can comprise a nitrogen-containing polymer, such aspolypyrrole or polyaniline. The sensing layer can additionally oralternatively be composed of any appropriate conductive material. Inanother example, the sensing layer can additionally or alternativelycomprise a protein or peptide serving as a complementary molecule to ananalyte, such as glucose oxidase for glucose sensing or valinomycin forpotassium sensing. In variations of this example, the sensing layer cancomprise amino acids (e.g., lysine) and/or polymer chains ofsubsequently associated amino acids (e.g., poly-lysine). In providing aprotein distribution, an amino acid distribution, a polymer chaindistribution, and/or any other particle distribution at the sensinglayer in Block S240, the distribution can be uniform or non-uniform(e.g., concentrated in desired regions, concentrated at a surface,etc.), homogenous or heterogeneous, and generated in any suitablemanner.

In some variations, Block S240 can include forming a notch at least atone sharp protrusion (i.e., sharp tip) of the array of sharp protrusionsS242 formed, as in Block S211 a. The notch, as shown in FIG. 9 , can beused as a pocket to isolate the sensing layer, and can additionally oralternatively be filled with any other suitable functional material. Inone such variation, the notch can be filled with a protective materialthat functions to protect the sensing layer during insertion or during aperiod of contact with the user's body fluid. In another variation, thenotch can be filled with a “calibration material” configured to provideor release an analyte according to a known profile (e.g., releaseprofile, concentration, degradation profile, etc.). In anothervariation, the notch can be filled with a therapeutic substance tofacilitate delivery of the therapeutic substance to a user in a drugdelivery application. The notch can be formed in alignment with a sharptip of a filament, or can alternatively be form in misalignment with awarp tip of a filament. Variations of Block S240 can entirely omitforming the notch, or can including providing a notch for any othersuitable purpose.

Some variations of the method can further include Block S245, whichrecites: coupling an intermediate selective layer to the conductivelayer defined in Block S220. In a variation wherein another layer (e.g.,an intermediate active layer that facilitates transduction, as describedin Section 1 above) is coupled superficial to the conductive layerdefined in Block S220, the method can include a variation of Block S245as Block S246, which recites: providing an intermediate selective layerable to transmit a signal to the conductive layer, and coupling thesensing layer defined in Block S240 to the intermediate selective layer.Blocks S245 and S246 function to provide an additional selective layerto facilitate detection of an analyte (e.g., glucose) in a selectivemanner. In some variations, Blocks S245 and S246 can include applying apolymer superficial to the conductive layer, and polymerizing thepolymer to set the intermediate selective layer. In specific examples ofBlocks S245 and S246, the intermediate selective layer can includephenylenediamine for glucose sensing, which is electropolymerized to setthe intermediate selective layer. Other variations of these specificexamples can include polymerization of any other suitable material inany other suitable manner (e.g., chemical polymerization, heatpolymerization, photopolymerization, etc.). Other variations of BlocksS245 and S246 can alternatively include providing a non-polymericmaterial as the intermediate sensing layer, which can be processed inany other suitable manner.

Block S250 recites forming a selective layer, and functions to form alayer configured to facilitate sensing of specific target analytes.Preferably, Block S250 comprises forming a selective layer comprising apolymer matrix with a distribution of complementary molecules S252 to atleast one target analyte characterizing a user's body chemistry. BlockS252 preferably comprises forming a homogenous mixture of the polymermatrix material (e.g., in either a solution or gel phase) with thedistribution of complementary molecules, but can alternatively compriseforming a heterogeneous mixture of the polymer matrix material with thedistribution of complementary molecules. Alternatively, Block S252 canbe replaced by Block S254, which comprises depositing a layer of apolymer matrix and depositing the distribution of complementarymolecules, onto the assembly produced after Block S240, in any order. Instill another alternative, Block S250, S252 and/or Block S254 can beperformed prior to one or more of Blocks S220, S230, and S240, such thata selective layer is deposited at different times and/or differentlocations during processing of the microsensor. In one such example, ina sensor for glucose detection applications, Block S250 is performedsubsequent to Block S220 (e.g., immediately over the conductive layer).In another example, with a conductive substrate, Block S250 can beperformed subsequent to Block S210 (e.g., a selective layer can bedeposited onto a tip region of the conductive substrate). Forming aselective layer comprising a polymer matrix can further comprise forminga selective layer with a polymer matrix and a plasticizer, inembodiments wherein a flexible polymer matrix is desired for Block S250.In one specific example, the polymer matrix comprises polyvinyl chloride(PVC) with a plasticizer to increase flexibility; however, in othervariations, the polymer matrix can be composed of any appropriatepolymer (e.g., polyethylene, polytetrafluoroethylene, urethane,polyurethane, phenylenediamine, ortho-phenylenediamine, proteinmatrices, amino acid matrices, etc.), with or without a plasticizer, andconfigured to contain a distribution of complementary molecules. Again,in one example, the distribution of complementary molecules comprisesglucose oxidase molecules for glucose sensing, and in another example,the distribution of complementary molecules comprises valinomycinmolecules for potassium sensing. Block S250 can be performed by spincoating a polymer matrix-complementary molecule mixture with or withouta plasticizer, by drop casting a polymer matrix-complementary moleculemixture with or without a plasticizer, or by any appropriate method.Additionally, spin coating, drop casting, electrodeposition,electroplating, or any other suitable method of application can beperformed in stages, such that the selective layer is characterized by atunable thickness. The tunable thickness preferably governs a rate atwhich complementary molecules bind to target analytes (e.g., diffusionrate), and governs the amount (e.g., concentration or total amount) ofcomplementary molecules within the selective layer and/or defines amolecular size cut-off.

In some variations, in particular, variations of manufacturing amicrosensor for glucose sensing, the method 200 can additionally oralternatively include Block S256, which recites: providing a stabilizinglayer configured to stabilize the sensing layer. Block S256 preferablyfunctions to stabilize a glucose oxidase sensing layer, in manufacturinga microsensor for glucose sensing; however, Block S256 can additionallyor alternatively function to stabilize the sensing layer for any othersuitable application. In some variations, Block S256 can includeproviding a polymer superficial to the sensing layer, and polymerizingthe polymer to set the intermediate selective layer. In specificexamples of Block S256, the stabilizing layer can includephenylenediamine for glucose sensing, which is electropolymerized to setthe stabilizing layer. Other variations of this specific example caninclude polymerization of any other suitable material in any othersuitable manner (e.g., chemical polymerization, heat polymerization,photopolymerization, etc.). Other variations of Block S256 canalternatively include providing a non-polymeric material as theintermediate sensing layer, which can be processed in any other suitablemanner.

In some variations, in particular, variations of manufacturing amicrosensor for glucose sensing, the method 200 can additionally oralternatively include Block S258, which recites: providing anintermediate protective layer superficial to the sensing layer. BlockS258 preferably functions to form a layer that provides intermediateprotection and/or block transport of undesired species. In somevariations, Block S258 can include providing a polymer superficial tothe sensing layer, including at least one functional compound configuredto provide a protective barrier. In examples, the polymer of theintermediate protective layer can include any one or more of: teflon,chlorinated polymer, nafion, polyethylene glycol, and any other suitablepolymer, and can include functional compounds including one or more of:lipids, charged chemical species that block transport of chargedspecies, surfactants, and any other suitable compound. Other variationsof Block S258 can alternatively include providing a non-polymericmaterial as the intermediate protective layer, which can be processed inany other suitable manner.

The method 200 can additionally or alternatively include any othersuitable Blocks or Steps configured to generate an array of filamentsfor analyte sensing during contact with a body fluid of the user. Assuch, the method 200 can include any one or more of: coupling anadhesion layer to any suitable layer used during the method, wherein theadhesion layer functions to facilitate maintenance of coupling of thelayer(s) for robustness; coupling a temporary functional layer to theselective layer, which facilitates penetration into the body of the userand/or calibration of the microsensor; providing a functional externallayer configured to suppress or prevent an inflammatory response (e.g.,by comprising a surface treatment or an anti-inflammatory agent),prevent bio-rejection, prevent encapsulation (e.g., by comprising abio-inert substance, such as pyrolytic carbon), enhance targetanalyte/ion detection, and/or provide any other suitable anti-failuremechanism; and processing the substrate according to any other suitableprocess.

The FIGURES illustrate the architecture, functionality and operation ofpossible implementations of systems, methods and computer programproducts according to preferred embodiments, example configurations, andvariations thereof. In this regard, each block in the flowchart or blockdiagrams may represent a module, segment, step, or portion of code,which comprises one or more executable instructions for implementing thespecified logical function(s). It should also be noted that, in somealternative implementations, the functions noted in the block can occurout of the order noted in the FIGURES. For example, two blocks shown insuccession may, in fact, be executed substantially concurrently, or theblocks may sometimes be executed in the reverse order, depending uponthe functionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts, or combinations of special purpose hardware andcomputer instructions.

The present application is related to U.S. patent application Ser. No.16/722,977 filed Dec. 20, 2019, which is a continuation of U.S. patentapplication Ser. No. 14/876,692 filed 6 Oct. 2015, which is acontinuation of U.S. patent application Ser. No. 14/211,404, filed 14Mar. 2014, which claims the benefit of U.S. Provisional Application Ser.No. 61/905,583, filed on 18 Nov. 2013 and U.S. Provisional ApplicationSer. No. 61/781,754, filed on 14 Mar. 2013, which are all incorporatedherein in their entirety by reference.

As a person skilled in the art will recognize from the previous detaileddescription and from the figures and claims, modifications and changescan be made to the preferred embodiments of the invention withoutdeparting from the scope of this invention defined in the followingclaims.

What is claimed is:
 1. A method for manufacturing analyte sensingmicroneedles, the method comprising: removing material from needlebodies to form sharp tips of microneedles; and forming at least onelayer along at least one of the sharp tips of a respective one of themicroneedles, which has an electrically conductive inner portion and anelectrically insulating material surrounding the electrically conductiveinner portion, wherein the insulating material defines an outerskin-contacting surface of the respective microneedles and exposes theat least one layer is configured to detect at least one analyte ininterstitial fluid when the microneedles are positioned within a user'sskin.
 2. The method of claim 1, wherein the electrically conductiveinner portion defines an active region between the electricallyinsulating material and an apex of the at least one of the sharp tips,wherein the at least one layer extends along the active region.
 3. Themethod of claim 1, wherein the electrically insulating material is anoxide layer.
 4. The method of claim 1, wherein the at least one layerextends along a sloped region of the electrically conductive innerportion, wherein the sloped region is between an apex of the at leastone of the sharp tips and the electrically insulating material.
 5. Themethod of claim 1, further comprising removing the material from theelectrically conductive inner portion via an etching process or cuttingprocess.
 6. The method of claim 1, wherein the at least one layer isconfigured to remain coupled to the respective needle body for insertioninto the user's skin.
 7. The method of claim 1, wherein when themicroneedles extend into the user's tissue, the microneedles areconfigured to detect analytes on opposing sides of their respectivesharp tips.
 8. The method of claim 1, further comprising punching,die-cutting, and/or water cutting a substrate connecting themicroneedles.
 9. The method of claim 1, wherein a substrate connectingthe microneedles includes at least one of a semiconducting material, aconducting material, or an insulating material.
 10. The method of claim1, further comprising electrically coupling the microneedles to anelectronics circuit.
 11. The method of claim 1, wherein one or more themicroneedles has a height within a range from 150 microns to 500microns.
 12. The method of claim 1, wherein a width of a gap betweenadjacent microneedles is less than a diameter of one of the adjacentmicroneedles.
 13. The method of claim 1, wherein forming the at leastone layer includes applying a plurality of layers to a sloped surface ofthe at least one of the sharp tips.
 14. A method for manufacturing amicroneedle sensor, the method comprising: removing material from needlebodies to form sharp ends; and forming at least one layer along each ofthe sharp ends of the needle bodies, wherein the at least one layer isconfigured to facilitate detection of at least one analyte ininterstitial fluid, wherein the needle bodies each include a conductivematerial and an electrically insulating material electrical insulatingthe conductive material, wherein the conductive material is electricallycoupled to the at least one layer to transmit signals, wherein theinsulating material defines an outer skin-contacting surface of therespective microneedles, and wherein the sharp end protrudes away from abase of the needle body and past the outer skin-contacting surface. 15.The method of claim 14, wherein the electrically insulating material isan oxide.
 16. The method of claim 14, further comprising removing thematerial from the from needle bodies using an etching process or acutting process.
 17. The method of claim 14, further comprising formingone or more layers across a pointed tip of the sharp end.
 18. A methodfor manufacturing a microneedle sensor, the method comprising: removingmaterial from a semiconductor substrate to form needle bodies havingsharp ends with exposed conductive material; and after forming the sharpends, forming at least one analyte detection layer along conductivematerial of the needle bodies, wherein the at least one layer isconfigured to facilitate detection of at least one analyte ininterstitial fluid of a user, wherein the needle bodies each include aconductive material and an electrically insulating material thatelectrical insulates the conductive material, wherein the electricallyinsulating material defines an outer skin-contacting surface and atleast a portion of the sharp end protruding past the outerskin-contacting surface.
 19. The method of claim 18, further comprisingapplying an insulating material along at least one of the needle bodies.20. The method of claim 18, further comprising using an etching processto remove the material from the semiconductor substrate.
 21. The methodof claim 18, further comprising using a laser etching process to removethe material from the semiconductor substrate.
 22. The method of claim18, further comprising punching, die-cutting, laser cutting, molding,and/or water cutting the semiconductor substrate to form at least aportion of the microneedles, wherein the at least one analyte detectionlayer is formed along the exposed conductive material of the needlebodies.
 23. A method for manufacturing an analyte sensor withmicroneedles, the method comprising: removing material from a substrateto form an array of needle bodies and tissue-piercing tips; and applyingat least one detection material to each of the tissue-piercing tips,wherein the at least one detection material is configured to react withat least one analyte in interstitial fluid when the tissue-piercing tipsare located in a user's tissue, wherein at least one of the needlebodies includes a conductive material and an electrically insulatingmaterial that electrically insulates the conductive material, whereinthe insulating material defines an outer skin-contacting surface, andwherein at least a portion of sharp end of the needle bodies protrudespast the outer skin-contacting surface.
 24. The method of claim 23,further comprising applying at least an insulating layer along sidewallsof each of the microneedles.
 25. The method of claim 23, furthercomprising forming a plurality of layers located on a sidewall of theneedle bodies, and the plurality of layers include a conductive layerand an insulating layer.
 26. An analyte sensor product for detecting atleast one analyte, wherein the analyte sensor product is made by aprocess comprising: removing material from a semiconductor substrate toform needle bodies with sharp ends with exposed conductive material; andafter forming the sharp ends, forming at least one analyte detectionlayer along the exposed conductive material, wherein the at least onelayer is configured to facilitate detection of at least one analyte ininterstitial fluid of a user, wherein at least one of the needle bodiesincludes a conductive material and an electrically insulating materialthat electrically insulates the conductive material, wherein theelectrically insulating material defines an outer skin-contactingsurface, and wherein at least a portion of the sharp end protrudes pastthe outer skin-contacting surface.
 27. The analyte sensor product ofclaim 26, wherein the process includes forming a plurality of layers ona sidewall of the needle bodies, and the plurality of layers include atleast one conductive layer and at least one insulating layer.